In this video frame grab provided by LifeNews via Rossia 24 TV channel, which has been authenticated based on its contents and other AP reporting, former National Security Agency systems analyst Edward Snowden looks over his shoulder during a boat trip on the Moscow River in Moscow.

BERLIN — Edward Snowden is calling for international help to persuade the U.S. to drop its espionage charges against him, according to a letter a German lawmaker released Friday after he met the American in Moscow.

U.S. Secretary of State John Kerry, meanwhile, has conceded that some of the NSA’s spying has reached too far and will be stopped.

Snowden said he would like to testify before the U.S. Congress about National Security Agency surveillance and may be willing to help German officials investigate alleged U.S. spying in Germany, Hans-Christian Stroebele, a lawmaker with Germany’s opposition Greens, told a news conference.

But Snowden indicated in the letter that neither would happen unless the U.S. dropped its espionage charges — a policy shift the Obama administration has given no indication it would make.

Stroebele’s meeting with Snowden on Thursday took place a week after explosive allegations from the Der Spiegel news magazine that the NSA monitored Chancellor Angela Merkel’s cellphone prompted her to complain personally to President Barack Obama. The alleged spying has produced the most serious diplomatic tensions between the two allies since Germany opposed the U.S.-led invasion of Iraq in 2003.

Germany’s top security official said he would like to arrange for German authorities to talk to Snowden about those allegations and other U.S. surveillance operations that have enraged Europeans.

Snowden has said he no longer has the NSA materials but his knowledge of U.S. spying efforts could be seen as invaluable by other nations.

“He pointed out that he was active in the U.S. secret services, the NSA and CIA, not just as an administrator or something like that who had access to computers, but also ... participated in operations,” Stroebele said of Snowden.

“He noted that he knows a lot about the inner structure ... that means he can, above all, interpret and explain all the documents... He could explain authentically only as an NSA man could. That means he is a significant witness for Germany, too.”

In his one-page typed letter, written in English and bearing signatures that Stroebele said were his own and Snowden’s, Snowden complained that the U.S. government “continues to treat dissent as defection, and seeks to criminalize political speech with felony charges that provide no defense.”

“I am confident that with the support of the international community, the government of the United States will abandon this harmful behavior,” Snowden wrote.

But he indicated he wouldn’t talk in Germany or elsewhere until “the situation is resolved.”

Stroebele said Snowden appeared healthy and cheerful during their meeting at an undisclosed location in Moscow. The German television network ARD, which accompanied Stroebele, said the Germans were taken to the meeting by unidentified “security officials” under “strict secrecy.”

Snowden “said that he would like most to lay the facts on the table before a committee of the U.S. Congress and explain them,” Stroebele said. The lawmaker, a prominent critic of the NSA’s alleged activities, said the 30-year-old “did not present himself to me as anti-American or anything like that — quite the contrary.”